threadseries designation: (UN, UNC, UNF, UNEF, UNS) The thread series is generally relative to the outside diameter of the screw. 20 threads per inch on a 1/4" diameter screw is considered coarse: 1/4-20 UNC. On a 3/4" diameter screw, 20 threads per inch is considered extra-fine: 3/4-20 UNEF. Frommy experience, the closest drill bit size to a 5/16″-18 tap is 17/64, which lines up with an F drill bit. You can also use basic math to determine the relative drill bit size. We concluded that it was the closest bit because 17/64 is so close to the 5/16′′-18 (DH=.2583) tap when divided. 15TAP DRILL SIZES - UNIFIED THREAD MILLS Size Threads Per Inch Minor Diameter Tap Drill Diameter (Cutting Tap) 5/16 18 - - - .2520 .2650 .2630 .2548 .2584 .2620 .2656 .2692 Threads Per Inch Minor Diameter Tap Drill Diameter (Cutting Tap) UNC UNF UNEF UN Min. 2B&3B Max. 2B Max. 3B 80% Thread 75% Thread 70% Thread 65% TapDrill Sizes for 11/16 - 16 16-UN. If not specified, assume a thread depth of 75%. You can learn more about thread depth in tapping here. To get the tap drill size in other depths, use our Tap Drill Size Calculator . Thread Depth Tap Drill Size (Inch) (UNC/UNF/UNEF) National Pipe (NPT) Dryseal Pipe (BPTF) British Pipe (BSP) ACME Note1: Default value is 65 % .. Note 2: The diameter of the drilled holes will be oversize in most materials.If the checkbox is ticked, the effect of drill oversize will be taken into account in tap drill bit selection Amount of expected drill oversize is calculated according to table given in page 897 of Machinery's Handbook, 29th. 916"-18 UNF HSS Plug Tap, Qualtech. Find this item and other cutting tools on DrillsandCutters.com. Toggle menu. FREE Two-Day Shipping on orders over $100 Compare ; Cart. Search. Categories. Drill Bits . Jobber Drills (Standard Length) Black & Gold (KFD) Jobber Drills, Premium; Cobalt Jobber Drills; Black & Gold HSS Contractor Differentsubscription plans provide distinct categories of support. Find out the level of support for your plan. View levels of support. Users reported that the ANSI 9/16 - 18 UNF Internal Tap drill size is larger than the MAX minor diameter allowed. Calculatinga tap drill size-.975 divided by the pitch(18 in your case) yields the double depth of the thread,which for an 18 pitch would be .054" Subtract the double depth (.054) from the major diameter(11/16 or .6875" in your case) and the result would be the tap hole size which here would be .633". 1Ypyrk.

9 16 18 unf tap drill size